An Experimental Study of Turbulent Flow in a Spiral-Groove Configuration

1968 ◽  
Vol 90 (2) ◽  
pp. 443-449 ◽  
Author(s):  
R. A. Burton
Keyword(s):  
Large Scale ◽  
Reynolds Numbers ◽  
Operating Conditions ◽  
Working Fluid ◽  
Inertial Effects ◽  
Spiral Groove ◽  
Experimental Apparatus ◽  
Machine Elements ◽  
Made In

Pressure and velocity data are reported for measurements in a large-scale experimental apparatus, designed to act as a model of a spiral-groove configuration operating at turbulent Reynolds numbers, and using air as a working fluid. The results predict that inertial effects at the steps in film thickness will exert a dominant influence on flows in machine elements made in geometric similitude to the model. Negative gage pressures were indicated in the thin-film regions, and these would be expected to lead at times to film breakup in elements using a liquid as the working fluid. Furthermore, negative stiffness under displacement of the journal was indicated for some operating conditions. The results, taken together, indicate the role of inertial effects, and dangerous operating conditions as to film breakup and loss of load support.

scholarly journals A Protocol for Extraction of Infective Viromes Suitable for Metagenomics Sequencing from Low Volume Fecal Samples

Viruses ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 667 ◽  
Author(s):  
Ling Deng ◽  
Ronalds Silins ◽  
Josué L. Castro-Mejía ◽  
Witold Kot ◽  
Leon Jessen ◽  
...  
Keyword(s):  
Genome Sequencing ◽  
Large Scale ◽  
Metagenomic Sequencing ◽  
High Input ◽  
Human Gut ◽  
Specific Host ◽  
Substantial Progress ◽  
Low Volume ◽  
Made In

The human gut microbiome (GM) plays an important role in human health and diseases. However, while substantial progress has been made in understanding the role of bacterial inhabitants of the gut, much less is known regarding the viral component of the GM. Bacteriophages (phages) are viruses attacking specific host bacteria and likely play important roles in shaping the GM. Although metagenomic approaches have led to the discoveries of many new viruses, they remain largely uncultured as their hosts have not been identified, which hampers our understanding of their biological roles. Existing protocols for isolation of viromes generally require relatively high input volumes and are generally more focused on extracting nucleic acids of good quality and purity for down-stream analysis, and less on purifying viruses with infective capacity. In this study, we report the development of an efficient protocol requiring low sample input yielding purified viromes containing phages that are still infective, which also are of sufficient purity for genome sequencing. We validated the method through spiking known phages followed by plaque assays, qPCR, and metagenomic sequencing. The protocol should facilitate the process of culturing novel viruses from the gut as well as large scale studies on gut viromes.

scholarly journals Cosmic Inflation, Quantum Information and the Pioneering Role of John S Bell in Cosmology

Universe ◽  
2019 ◽  
Vol 5 (4) ◽  
pp. 92 ◽  
Author(s):  
Jérôme Martin
Keyword(s):  
Quantum Mechanics ◽  
Quantum Information ◽  
Large Scale ◽  
Gravitational Instability ◽  
Cosmic Inflation ◽  
Large Scale Structures ◽  
Scale Structures ◽  
Accuracy Data ◽  
Made In

According to the theory of cosmic inflation, the large scale structures observed in our Universe (galaxies, clusters of galaxies, Cosmic Background Microwave—CMB—anisotropy...) are of quantum mechanical origin. They are nothing but vacuum fluctuations, stretched to cosmological scales by the cosmic expansion and amplified by gravitational instability. At the end of inflation, these perturbations are placed in a two-mode squeezed state with the strongest squeezing ever produced in Nature (much larger than anything that can be made in the laboratory on Earth). This article studies whether astrophysical observations could unambiguously reveal this quantum origin by borrowing ideas from quantum information theory. It is argued that some of the tools needed to carry out this task have been discussed long ago by J. Bell in a, so far, largely unrecognized contribution. A detailled study of his paper and of the criticisms that have been put forward against his work is presented. Although J. Bell could not have realized it when he wrote his letter since the quantum state of cosmological perturbations was not yet fully characterized at that time, it is also shown that Cosmology and cosmic inflation represent the most interesting frameworks to apply the concepts he investigated. This confirms that cosmic inflation is not only a successful paradigm to understand the early Universe. It is also the only situation in Physics where one crucially needs General Relativity and Quantum Mechanics to derive the predictions of a theory and, where, at the same time, we have high-accuracy data to test these predictions, making inflation a playground of utmost importance to discuss foundational issues in Quantum Mechanics.

Weak Extinction Limits of Large-Scale Flameholders

1992 ◽  
Vol 114 (4) ◽  
pp. 776-782 ◽  
Author(s):  
M. R. Baxter ◽  
A. H. Lefebvre
Keyword(s):  
Large Scale ◽  
Liquid Hydrocarbon ◽  
Operating Conditions ◽  
Extinction Data ◽  
Jet Engine ◽  
Lean Blowout ◽  
Stirred Reactor ◽  
Experimental Apparatus ◽  
Varied Composition ◽  
Engine Systems

Weak extinction data obtained from an experimental apparatus designed to simulate the characteristics of practical afterburner combustion systems are presented. The apparatus supplies mixtures of varied composition (equivalence ratio and degree of vitiation), temperature and velocity to Vee-gutter flame holders of various widths and shapes similar to those found in jet engine systems. The fuel employed is a liquid hydrocarbon whose chemical composition and physical properties correspond to those of aviation kerosine, JP5. An equation for predicting weak extinction limits which accounts for upstream vitiation and the chemical characteristics of the fuel is derived from stirred reactor theory. The correlation between the predictions and experimental results indicates that the stirred reactor approach can provide a framework for predicting the lean blowout limits of practical flameholders over wide ranges of engine operating conditions.

scholarly journals Experimental Investigation of a Small-Scale ORC Power Plant Using a Positive Displacement Expander with and without a Regenerator

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1452 ◽  
Author(s):  
Collings ◽  
Mckeown ◽  
Wang ◽  
Yu
Keyword(s):  
Heat Exchanger ◽  
Power Plants ◽  
Large Scale ◽  
Internal Heat ◽  
Expansion Ratio ◽  
Operating Conditions ◽  
Working Fluid ◽  
Small Scale ◽  
Regenerative Heat ◽  
Positive Displacement

While large-scale ORC power plants are a relatively mature technology, their application to small-scale power plants (i.e., below 10 kW) still encounters some technical challenges. Positive displacement expanders are mostly used for such small-scale applications. However, their built-in expansion ratios are often smaller than the expansion ratio required for the maximum utilisation of heat sources, leading to under expansion and consequently higher enthalpy at the outlet of the expander, and ultimately resulting in a lower thermal efficiency. In order to overcome this issue, one possible solution is to introduce an internal heat exchanger (i.e., the so-called regenerator) to recover the enthalpy exiting the expander and use it to pre-heat the liquid working fluid before it enters the evaporator. In this paper, a small-scale experimental rig (with 1-kW rated power) was designed and built that is capable of switching between regenerative and non-regenerative modes, using R245fa as the working fluid. It has been tested under various operating conditions, and the results reveal that the regenerative heat exchanger can recover a considerable amount of heat when under expansion occurs, increasing the cycle efficiency.

scholarly journals Building a collaborative Psychological Science: Lessons learned from ManyBabies 1

2019 ◽  
Author(s):  
Krista Byers-Heinlein ◽  
Christina Bergmann ◽  
Catherine Davies ◽  
Michael C. Frank ◽  
Kiley Hamlin ◽  
...  
Keyword(s):  
Large Scale ◽  
Organizational Structures ◽  
Open Science ◽  
Lessons Learned ◽  
Psychological Science ◽  
Difficult Challenge ◽  
Implementation Data ◽  
Successes And Challenges ◽  
Made In

The field of infancy research faces a difficult challenge: some questions require samples that are simply too large for any one lab to recruit and test. ManyBabies aims to address this problem by forming large-scale collaborations on key theoretical questions in developmental science, while promoting the uptake of Open Science practices. Here, we look back on the first project completed under the ManyBabies umbrella – ManyBabies 1 – which tested the development of infant-directed speech preference. Our goal is to share the lessons learned over the course of the project and to articulate our vision for the role of large-scale collaborations in the field. First, we consider the decisions made in scaling up experimental research for a collaboration involving 100+ researchers and 70+ labs. Next, we discuss successes and challenges over the course of the project, including: protocol design and implementation, data analysis, organizational structures and collaborative workflows, securing funding, and encouraging broad participation in the project. Finally, we discuss the benefits we see both in ongoing ManyBabies projects and in future large-scale collaborations in general, with a particular eye towards developing best practices and increasing growth and diversity in infancy research and psychological science in general. Throughout the paper, we include first-hand narrative experiences, in order to illustrate the perspectives of researchers playing different roles within the project. While this project focused on the unique challenges of infant research, many of the insights we gained can be applied to large-scale collaborations across the broader field of psychology.

Management of Papermill Wastes: The Role of Filamentous Microorganisms as Indicators

1994 ◽  
Vol 29 (7) ◽  
pp. 185-188 ◽  
Author(s):  
L. Cingolani ◽  
E. Ciccarelli ◽  
M. Cossignani ◽  
Q. Tornari ◽  
V. Scarlata
Keyword(s):  
Statistical Analysis ◽  
Activated Sludge ◽  
Nutrient Deficiency ◽  
High Load ◽  
Operating Conditions ◽  
Sludge Treatment ◽  
Filamentous Microorganisms ◽  
Made In

A study was made at nine papermill activated sludge treatment plants, affected by bulking phenomena, on the behaviour of filamentous microorganisms in connection with plant performances. In the sludge samples 24 organisms were identified, the most frequently observed being type 0041 and 0675. The principal causes of inconvenience, isolated through statistical analysis, were identified as low oxygenation, high load, low F/M, nutrient deficiency. Changes made in operating conditions improved bulking in some plants.

scholarly journals Irrigation in the Ili River Basin of Central Asia: From Ditches to Dams and Diversion

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1650 ◽  
Author(s):  
Steven Pueppke ◽  
Qingling Zhang ◽  
Sabir Nurtazin
Keyword(s):  
Iron Age ◽  
Large Scale ◽  
New Technologies ◽  
18Th Century ◽  
Irrigated Agriculture ◽  
Ili River Basin ◽  
The 1960S ◽  
The 19Th Century ◽  
Made In

Central Asia’s Ili River is fed by mountain streams that flow down into an isolated and arid basin that today is shared by Kazakhstan and China. Agriculture in the basin is dependent upon irrigation, which was practiced as long ago as the Iron Age, when early pastoralists constructed ditches to channel water from streams onto nearby fields. Irrigation had become much more common by the 18th century, when the region was controlled by the Dzungarian Khanate. The khanate was toppled by the Qing Chinese in the 1750s in the first of a series of confrontations that destroyed and then rebuilt the basin’s agricultural economy. The region has since been dominated by a succession of Chinese and Russian (and later Soviet and independent Kazakh) governments, each of which recognized the essential role of irrigated agriculture in maintaining control. Thus every cycle of destruction led to reclamation of new lands, resettlement of farmers and upgrading of infrastructure to expand irrigation. This allowed an impressive diversity of fruits, vegetables and field crops to be grown, especially on loess soils of the more fertile upper basin, where tributaries could be easily tapped by gravity flow. Many of these tributaries were entirely diverted by the 19th century, so that they no longer reached the Ili. Large scale irrigation commenced in the 1960s, when the Soviets built Kapchagai dam and reservoir in the lower part of the basin and installed pumps to raise water from the Ili River onto nearby reclaimed sierozem soils, mostly for cultivation of rice. China later constructed a cluster of small- and medium-sized dams that enabled expansion of agriculture in the upper part of the basin. Many irrigated areas along the lower reaches of the Ili in Kazakhstan have been abandoned, but irrigation in the upper basin continues to expand. Declining soil fertility, salinization, pollution, insufficient inflows and adverse economic conditions currently challenge irrigation across the entire basin. Investments are being made in new technologies as a means to sustain irrigated agriculture in the basin, but it remains to be seen if these strategies will be successful.

The Effects of Turbulence and Stator/Rotor Interactions on Turbine Heat Transfer: Part I—Design Operating Conditions

1989 ◽  
Vol 111 (1) ◽  
pp. 87-96 ◽  
Author(s):  
M. F. Blair ◽  
R. P. Dring ◽  
H. D. Joslyn
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Finite Difference ◽  
Large Scale ◽  
Reynolds Numbers ◽  
Companion Paper ◽  
Operating Conditions ◽  
Strong Impact ◽  
Analytical Program ◽  
Turbine Model

A combined experimental and analytical program was conducted to examine the effects of inlet turbulence, stator–rotor axial spacing, and relative circumferential spacing of first and second stators on turbine airfoil heat transfer. The experimental portion of the study was conducted in a large-scale (approximately 5× engine), ambient temperature, stage-and-a half rotating turbine model. The data indicate that while turbine inlet turbulence can have a very strong impact on the first stator heat transfer, its impact in downstream rows is minimal. The effects on heat transfer produced by relatively large changes in stator/rotor spacing or by changing the relative row-to-row circumferential positions of stators were very small. Analytical results consist of airfoil heat transfer distributions computed with a finite-difference boundary layer code. Data obtained in this same model for various Reynolds numbers and rotor incidence angles are presented in a companion paper (Part II).

scholarly journals On the role of turbulent large-scale streaks in generating sediment ridges

2021 ◽  
Vol 930 ◽  
Author(s):  
Markus Scherer ◽  
Markus Uhlmann ◽  
Aman G. Kidanemariam ◽  
Michael Krayer
Keyword(s):  
Large Scale ◽  
Reynolds Numbers ◽  
Streamwise Velocity ◽  
Top Down ◽  
Outer Flow ◽  
Secondary Currents ◽  
Sediment Bed ◽  
Low Speed Streaks ◽  
O 10

The role of turbulent large-scale streaks or large-scale motions in forming subaqueous sediment ridges on an initially flat sediment bed is investigated with the aid of particle resolved direct numerical simulations of open channel flow at bulk Reynolds numbers up to 9500. The regular arrangement of quasi-streamwise ridges and troughs at a characteristic spanwise spacing between 1 and 1.5 times the mean fluid height is found to be a consequence of the spanwise organisation of turbulence in large-scale streamwise velocity streaks. Ridges predominantly appear in regions of weaker erosion below large-scale low-speed streaks and vice versa for troughs. The interaction between the dynamics of the large-scale streaks in the bulk flow and the evolution of sediment ridges on the sediment bed is best described as ‘top-down’ process, as the arrangement of the sediment bedforms is seen to adapt to changes in the outer flow with a time delay of several bulk time units. The observed ‘top-down’ interaction between the outer flow and the bed agrees fairly well with the conceptual model on causality in canonical channel flows proposed by Jiménez (J. Fluid Mech., vol. 842, 2018, P1, § 5.6). Mean secondary currents of Prandtl's second kind of comparable intensity and lateral spacing are found over developed sediment ridges and in single-phase smooth-wall channels alike in averages over ${O}(10)$ bulk time units. This indicates that the secondary flow commonly observed together with sediment ridges is the statistical footprint of the regularly organised large-scale streaks.

scholarly journals A Protocol for Extraction of Infective Viromes Suitable for Metagenomics Sequencing from Low Volume Fecal Samples

2019 ◽  
Author(s):  
Ling Deng ◽  
Ronalds Silins ◽  
Josue Leonardo Castro Mejia ◽  
Witold Kot ◽  
Leon Jessen ◽  
...  
Keyword(s):  
Genome Sequencing ◽  
Large Scale ◽  
Metagenomic Sequencing ◽  
High Input ◽  
Human Gut ◽  
Specific Host ◽  
Substantial Progress ◽  
Low Volume ◽  
Made In

The human gut microbiome (GM) plays an important role in human health and diseases. However, while substantial progress has been made in understanding the role of bacterial inhabitants of the gut, much less is known regarding the viral component of the GM. Bacteriophages (phages) are viruses attacking specific host bacteria and likely play important roles in shaping the GM. Although metagenomic approaches have led to the discoveries of many new viruses, they largely remain uncultured as their hosts have not been identified, which hampers our understanding of their biological roles. Existing protocols for isolation of viromes generally require relatively high input volumes and are generally more focused on extracting nucleic acids of good quality and purity for down-stream analysis and less on purification of still infective viruses. Here we report the development of an efficient protocol requiring low sample input yielding purified viromes containing still infective phages which also are of sufficient purity for genome sequencing. We validated the method through spiking of known phages followed by plaque assays, qPCR and metagenomic sequencing. The protocol should facilitate the culturing of novel viruses from the gut as well as large scale studies on gut viromes.

Sign in / Sign up

Export Citation Format

Share Document